The present invention relates to an improved drill bit for oil and gas well applications. Typically, conventional drill bits employ a plurality of depending cones and each cone carries a great number of cutting surfaces thereon. These cones are rotatably attached to the drill bit body upon axels radially arranged about the central axis of the drill bit and are disposed to engage the bottom of the borehole.
In operation, rotation is imparted to the drill string which extends from the surface down the borehole to the drill bit. The body of the drill bit is thereby rotated and the cones which press against the bottom of the borehole spin about their axes, usually about sealed bearings, as the bit body is rotated. The cutting surfaces of these spinning cones free bits of the rock formation as they roll across the floor of the borehole.
The problem addressed by the present invention is the removal of the cuttings from the base of the borehole once they have been freed from the formation. If these cuttings are not effectively removed, the cutting surfaces upon the cones operate only to further pulverize previous cuttings and are prevented from effectively biting into the formation as necessary to advance the drilling.
It is conventional to pump a stream of mud through the drill string, through the bores and conduits in the main body of the drill bit, and to expell this mud downwardly from the body of the drill bit at the cones. The mud delivered through the drill bit performs several functions in that it cools the bit, stabilizes the borehole, holds the drill bit and drill string within the borehole by equalizing the pressure on the bit and, most important to the present invention, the current of mud is intended to sweep away the cuttings at the cones.
The present invention addresses the efficiency of flushing the cuttings away and also addresses two problems attendant the prior art solution, the problems of well bore and drill string erosion. Drill string erosion is introduced by the use of the mud flow and refers to the abnormally high rate of wear at the drill string adjacent the drill bit caused by the abrasion of particles and cuttings within the flow of mud. A similar problem is erosion of the borehole itself caused by the flow of mud and abrasive particles returning up the borehole about the drill bit.